Hot drinks are often prepared by appliances having a water container with an outlet from which, via a heating device and a riser, water heated by the heating device or steam can be supplied to a brewing or mixing device wherein the water in the riser can be heated by the heating device.
Such appliances operate on the so-called percolator principle whereby water in the riser is heated by the heating device and the vapor bubbles formed during the boiling process rise in the riser and entrain the water with them, which is then supplied to the brewing or mixing device for brewing coffee or for mixing with a powdery coffee, milk or meat stock extract.
The water container is in communication with the riser according to the principle of communicating pipes so that the water level in the riser depends on the respective filling level in the water container. This has the result that in particular when the filling level in the water container is high, there is a volume of water in the riser above the heating device, which is not heated or is only insufficiently heated when the appliance is started up after a shutdown. Thus, this cold water is conveyed to the brewing or mixing device by the vapor bubbles produced in the area of the heating device which results in a largely cold drink and in the case of a brewing device, an at least inadequate brewing of the material to be brewed.